Getter assembly



y 1, 1958 A. M. MORRELL ETAL 2,841,732

GETTER ASSEMBLY Filed Oct. 15, 1953 INVENTOR.

Alb er? M Mar/'61], 6 MCI/UM W////am 15. M/Z/er ATTORNEY 2,841,732ratented July 1', 1958 ler, Lancaster, Pa, assignors to Radio(Zorporation America, a corporation or llteinwarc Application @ctober15, 1953, Serial No. 386,2d2

9 tClainis. (Ci. Bid-"176) This invention relates to a getter assemblyWhich is particularly useful in degassing large electron tubes such ascathode ray tubes.

in the manufacture of electron tubes, one of the steps normally requiredto properly degas a tube consists in flashing a getter. A getter isprimarily a chemically active material, and usually includes one of thealkaline earth metals, which can be heated and voiatilized, after thetube has been evacuated to a desired degree, to absorb the remainingtraces of gas. The getter material, or gas clean-up agent, as it isfrequently called, may be carried by a metal trough having a highermelting point than the getter material. One or more getter troughs maybe connected across the legs or" a U-shaped wire support to form aclosed electrical loop. The getter loop so formed and supported withinthe tube envelope is heated by a high frequency induction coil tovolatilize or flash the getter material. (3n flashing, the gettermaterial combines with any residual gas, such as oxygen, which is notremoved by the mechanical pumps, and forms a deposit of the alkalineearth metal on the inner wall of the glass envelope.

Large electron tubes, such as cathode ray tubes require a considerableamount of getter material to prop erly degas the tube. This isespecially true of tri-color kinescopes of the kind containing threeguns. in such relatively complicated tubes, the use of a single getterloop, with one or more getter troughs, is usually unsatisfactory. In thefirst place, such a getter assembly is necessarily large and requires agreat amount of power to flash the getter. Secondly, it is difficult tocontrol the flash to prevent the getter material from being deposited onthe various electrode elements. Thirdly, the getter deposit isordinarily concentrated Within a relatively small area of the glassenvelope, whereas it is desirable to distribute the flash, and hence thedeposit, over as large an area as possible to provide better gasclean-up. Another reason why a single getter loop of the type discussedis not satisfactory is that if the getter loop is initially open, or isopened up during flashing because of mechanical failure or overheating,the getter will not flash, or cannot be ire-flashed.

It has therefore been customary to use a plurality of loop getters inlarge size cathode ray tubes. A common arrangement comprises two or moregetters mounted at the open end of the gun, i. e. remote from itscathode. The getters are arranged axially and transversely symmetricalwithin the tube neck Wth the plane of each getter loop parallel to theneck. axis. They must be flashed individually by a battery of inductioncoils, one for each getter, with the coil axis normal to the axis of theneck and hence normal to the plane of the getter loop.

Such plural-getter arrangements also have certain disadvantages. ln thefirst place, the getters must be separately flashed and, a given getterloop when in the flashing position is physically outside of theinduction coil, where the magnetic field is relatively weak, rather thanand within it where the field is strongest. As a consequence,considerable power is required to flash the getters. The spacing betweenthe separate coils and separate getters is quite critical. Further, itis impractical to use more than three loop getters in such anarrangement because of the wide coil-to-getter spacing required to groupmore than three coils about a relatively narrow tube neck. it is thenfan object of this invention to provide an improved getter assembly.

Another object is to provide a getter assembly which overcomes theproblems of critical getter-tcdnduction coil spacing.

it is a further object to provide a compact getter assembly which allowsuniform flashing of a relatively large amount of getter material with areduced amount of power.

it is a further object to provide a getter assembly adapted to beflashed in alternate ways.

The foregoing and related objects are achieved in accordance with theinvention by the provision of a getter assembly having a closed mainconductive loop, which carries getter material along all or most of itslength, and a plurality of auxiliary induction loops supported in planestransverse to the main loop by suitably shaped conductors which areconnected to the main loop at spaced intervals such that each auxiliaryloop has a portion common to the main or getter loop. This structure ismounted in the neclr or" a cathode ray tube, with the main getter loopcoaxial with the tube axis. When thus mounted, the main getter inductionloop may be flashed by a single induction coil coaxial With the tube.Alternatively, or additionally, the auxiliary induction loops may beflashed individually by induction coils oriented transverse to the tubeThe invention is described in greater detail in connection with theaccompanying single sheet of drawings wherein:

Fig. 1 is a sectional view of a 3-gun color kinescope incorporating animproved getter assembly within the invention, the tube being shown onthe pump;

Fig. 2 is an enlarged perspective view of the getter assembly of l; and

Fig. 3 is a perspective view of another form of getter assemblyaccording to the invention.

The three-gun lrinescope shown on the pump in Fig. 1 comprises a mainchamber 1, which will be understood tocontain a suitable screen-unit ortarget assembly, not shown, for a battery of three guns 3, S and 7 inthe dependent glass neck portion 9 of the tube envelope. The guns arehere shown arranged delta (A) fashion as in Schroeder 2,595,548. Theparticular gun assembly here shown. is similar to the one claimed byialbfill M. Morrell in ccpending application Serial No. 364,041, new U.S. Patent 2,752,529, wherein the guns terminate in a cylindricalstructure containing a number of upstanding pole pieces 13 which operateto maintain' the three electron beams 3b, 5b, 7b converged throughouttheir scanning movement. The structure 11 terminates in a disc 1.5containing apertures 15a for the separate beams, and which provides asupport for the getter assembly of the present invention.

As shown more clearly in Fig. 2 the getter supports comprise a number,in this case six, of U-shape conductors 1'7 disposed in l'rexagonalarray on the outer surface of the disc and secured thereto in an uprightposition as by clamps or welds The upright arms of each U areelectrically and mechanically coupled to the next adjacent U by metalstraps 21. A getter trough 23 is secured at its opposite ends, as byWelding to the upstanding arms of each U-shape support 17. The troughs23 here shown are of a conventional construction and comprise acylindrical sleeve formed of thin metal, such as nickel, having a highermelting point than the getter material which is contained therein. Thegetter material, not shown, may comprise a conventional mixture ofbarium, magnesium and aluminum, for example. The wall of each trough orsleeve 23 may be thinned down along its length or it may be providedwith a longitudinal slit 23s so that it will burst upon heating to expelthe getter material. The direction of the getter flash of course dependsupon the orientation of the thinned portion or slit in the sleeve ortrough. In the instant case the slits 23s face outwardly so that theflash is toward the wall of the neck 9 of the envelope.

As previously pointed out, the metal straps 21 about the upstanding armsof each of the U-shaped gettersupports 17 provide a series connectionbetween all of the getter troughs 23. This electrical path or maingetter induction loop is concentric with the axis of the tube, and it ispossible therefore to induce a current in it with a conventionalradio-frequency induction coil 25 disposed concentrically about theouter surface of the neck 9 in line with the getter array. It is alsopossible to couple into anyone of the individual or closed-U inductionloops with a radio frequency coil, not shown, whose axis is at rightangles to the tube neck.

Figure 3 shows an alternative form of getter structure which isespecially suitable for use in a tube having no apertured disk 15 ofFigure l as a means of support. The assembly comprises a main gettertrough in the form of a loop 31 and a supporter ring 33 spaced from eachother by lateral support rods 35 connected to the loop 31 and ring 33 atspaced intervals. The main getter-loop 31 here shown is a continuoustrough of ring form containing a getter material, not shown. Theauxiliary induction" loops are formed by adjacent support rods 35 andthe portions of the getter loop ill and support ring 33 therebetween.

Other modifications may be made in structural details which will adaptthe getter assembly to the particular tube and method of processing. Forexample, the

auxiliary loops themselves may carry additional getter material otherthan that carried by the main getter loop, thus providing a copioussupply of getter and permiting flashing from many directions.

Relatively little power is needed to flash the main or series loop ineither embodiment of the invention since current is inducted only insaid loop and not in the auxiliary or closed-U loops. Furthermore, themain loop is located concentrically with the coil where the magneticflux is most concentrated. Uniform flashing is achieved because thewhole getter is flashed at one time.

In the event that the main loop opens-up, for example by reason ofoverheating, the closed-U" or auxiliary loops may be availed of toprovide further flashing. This may be done by presenting an inductioncoil to each auxiliary loop. Moreover, should an open circuit occuralong the getter trough itself, the heating circuit through the mainloop can nevertheless be completed through the getter support shuntingthe particular open portion of the getter trough.

The advantages and novel features of the getterassemblies of the presentinvention are as follows:

A. Since the main getter loop, the tube neck and the radio frequencycoil are concentric with each other, there are no critical spacingproblems involved in obtaining the optimum amount of coupling toproperly degas and flash the getter.

B. Should the main getter loop open, due to excessive radio frequencypower or mechanical failure, or should it be necessary to reflash, it isstill possible to individually flash the getters by coupling into eachsmall getter loop with a radio frequency coil positioned at right anglesto the tube neck.

C. A relatively large number of getters and, therefore,

a large amount of gettering material may be placed in the tube in acompact assembly and with minimum amount of radio frequency powerrequired to degas and flash the getters, since only the getter stripitself and not the associated Wire loop is heated.

D. The time required to flash the getters is reduced since all getterswill flash at one time.

What is claimed is:

l. A getter assembly comprising a main vaporizable getter loop, aplurality of conductive portions secured to and forming with said maingetter loop closed auxiliary induction loops, each of said auxiliaryinduction loops including a different portion of said getter loop, saidauxiliary induction loops extending angularly from said getter loop.

A getter assembly comprising conductive material arranged to form a mainclosed induction loop, a plurality of auxiliary closed induction loops,separate portions of said main loop each forming a part of differentones of said auxiliary loops, each of said auxiliary loops includingconductive portions secured to and extending angularly from said mainloop, and a quantity of getter material forming part of said main loop.

3. The invention according to claim 2 wherein said quantity of gettermaterial also forms a part of said auxiliary loops.

4-. A getter assembly comprising conductive material arranged in a planeto form a main closed induction loop, a plurality of auxiliary closedinduction loops, each of said auxiliary loops including elongatedconductive portions secured to and disposed in a plane perpendicular tosaid main loop, and separate portions of said main loop each forming apart of different ones of said auxiliary loops, and a quantity of gettermaterial forming a part of said main loop.

5. The invention of claim 2 wherein said auxiliary loops includeadditional getter material.

6. A getter assembly comprising a closed main loop of conductivematerial adapted to have heating currents induced therein by a magneticfield directed normal to the plane of the loop, and a plurality ofauxiliary closed loops of conductive material spaced about said mainloop, each of said auxiliary loops including a separate portion commonto said main loop and including a U-shaped member defining a planetransverse to the plane of said main loop, said U-shaped member forminga closed loop with said separate portion whereby heating currents may beinduced in each of said auxiliary loops by a magnetic field directednormal to said auxiliary loop, and a quantity of getter material forminga part ofeach one of said portions common to said main and auxiliaryloops.

7. A getter assembly comprising a closed main loop of conductingmaterial adapted to have heating currents induced therein by a magneticfield directed normal to the plane of the loop, a conducting supportmember in a plane substantially parallel to said main loop, and aplurality of spaced support rods interconnecting said main loop and saidsupport member and forming a plurality of auxiliary closed electricalloops transverse to said main loop, and a quantity of getter materialforming a part of said main loop.

8. A getter assembly comprising a flat support member, a plurality ofLJ-shaped conducting members extending away from said support member andwith their bases on said support member, said U-shaped members beinginterconnected electrically and in substantially circular array, agetter trough connecting the legs of each of said U-shaped members, anda quantity of vaporizable getter material within said getter trough.

9. In an evacuable envelope having a central axis, a getter-assemblycomprising a plurality of U-shaped conductive elements symmetricallydisposed in spaced relationship about said central axis, separategetter- 5 6 containers constituted of conductive material supportedReferences Cited in the file of this patent between the arms of each ofsaid U-shaped elements, UNITED STATES PATENTS and conductive meansconnecting said U-shaped elements in series to permit simultaneousflashing of the getter- 1,590,352 Eglm June 1926 material in saidcontainers by currents induced in said 5 1,752,813 Ruggles 1930 a semblya magnetic field Dailey 1

